Abstract： AIM: To study the anti-tumor effect of recombinant Muc1-MBP protein in vivo. METHODS: Mice were immunized subcutaneously with different dose of Muc1-MBP protein 3 times at 2-weekly intervals. C.57 BL/6 mice were challenged with LLC1 cells by tail vein or ICR mice irradiated with X-ray injected MCF-7 cells at back 4 d after the third immunization. The tumor was striped and measured 3 weeks later. Histological analysis of tumor tissue was carried out with HE staining . Tumor infiltrating lymphoeytes subsets were detected by immunohistochemistry. RESULTS: After 21 d of LLC1 cell challenge, there was only 60% forming lung tumor nodules and total number 17 in high dose Muc1-MBP group, while there was 100% forming lung tumor nodules in low dose Muc1-MBP group and control group and total number of tumor nodules was 39 and 54 in low dose and control group respectively. The results showed that tumor growth using high dose MUC1 -MBP was obviously suppressed( P < 0.05 ) , without statistically difference in low dose group. After 21 d of MCF-7 cell challenge, the tumor formation rate in control group and low dose Muc1-MBP group was 100% (6/6), while 66.7% (4/6) mice formed tumors in high dose Muc1-MBP group. The volumes of tumor in control group, high dose group and low dose group were respectively( 142.8 ±70.2) , (54.5 ±46.7) and (96.14 ± 53.37) mm~3. There are significant tumor inhibitory effect in high dose Muc1-MBP(P < O. 05), but not in low dose Muc1-MBP, compared with that control group. The result showed that tumor growth using high dose Muc1-MBP was obviously suppressed( P <0.05 ), but low dose group were not significantly changed. A number of CD4~+ and CD8~+ T cells were infiltrated into cancerous tissue in Muc1-MBP group. CONCLUSION: Muc1-MBP protein vaccine can significantly suppress the growth of LLC1 lung cancer and MCF-7 breast cancer, and provide a basis for clinical research